''Ophiura ophiura'' or the serpent star is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

in the order

Ophiurida The Ophiurida are an order of echinoderms within the class Ophiuroidea. It includes the vast majority of living brittle stars. Characteristics Ophiurida have bursae for respiration and excretion, and dorsal and ventral arm shields are present a ...

. It is typically found on coastal

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

s around northwestern Europe.

Description

''Ophiura ophiura'' has a circular central disc up to 35 mm (1.5 in) wide and five radially arranged, narrow arms each up to long. The general colour is mottled reddish-brown with a paler underside. Both the top and the underside of the disc are covered with calcareous plates. The arms are joined to the top rather than the edge of the disc and further small, articulating plates allow the arms to bend from side to side. Small spines on the arms lie flat against the surface. Four larger plates occur across the root of each arm with the outer pair having a comb-like edge, with 20 to 30 fine papillae in each.''Ophiura ophiura'' (Linnaeus, 1758)
''National Museums of Northern Ireland''. Retrieved August 10, 2011. A pair of pores is seen between the underside plates at the root of the arms.A brittlestar - ''Ophiura ophiura''
''

Marine Life Information Network The Marine Life Information Network (MarLIN) is an information system for marine biodiversity for Great Britain and Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic O ...

''. Retrieved August 10, 2011. Five large mouth-shield plates are on the underside of the disc which surround the central mouth. The teeth are in a vertical row above each of the five jaws and about five mouth papillae are on each side of the jaw.Macrobenthos of the North Sea - Echinodermata
''Marine Species Identification Portal''. Retrieved August 10, 2011.

Distribution and habitat

''Ophiura ophiura'' is found on the sea floor in the northeast

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

and the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea, epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the ...

from

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...

and Sweden south to Madeira and the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

. It is found below low-tide mark in the

neritic zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

down about 200 m, on sandy bottoms. It shows a preference for sediments with a fine grain size and about 35% mud content. It is a common species with 20 to 50 individuals occurring per square metre in some years in the North Sea.

Biology

''Ophiura ophiura'' is an active brittle star, moving with a jerky swimming action of its legs and sometimes burrowing. It is a filter feeder, feeding on a wide range of food, but also a bottom-feeding

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other s ...

and detritivore. It can regenerate its arms if they are damaged or torn off. Sexual reproduction takes place during the summer. The larvae are the typical ophiopluteus larvae of brittle stars and later settle on the sea bed and develop into juveniles.

Ecology

The copepod, ''Parartotrogus richardi'', is an ectoparasite of ''O. ophiura''. In the Clyde sea fishery for scampi (''

Nephrops norvegicus ''Nephrops norvegicus'', known variously as the Norway lobster, Dublin Bay prawn, ' (compare langostino) or ''scampi'', is a slim, orange-pink lobster which grows up to long, and is "the most important commercial crustacean in Europe". It is n ...

'') in

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

, the unwanted

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s that get caught up in the trawl include ''O. ophiura'', as well as the starfish ''

Asterias rubens The common starfish, common sea star or sugar starfish (''Asterias rubens'') is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 ...

''. A study undertaken to discover the survival rate of these animals when discarded and returned to the water found that uninjured ''A. rubens'' had a mortality rate of 4%, whereas virtually all the ''O. ophiura'' died within 14 days, even when they were returned to the sea immediately after being caught. Another study examined the rate at which the discarded invertebrates sank to the bottom and their ultimate fates. ''O. ophiura'' sank relatively slowly and was preyed upon by seabirds, and the arms were eaten by fish. On the sea bed, a succession of benthic scavengers thrived on their remains with crangonid shrimps and crabs such as ''

Carcinus maenas ''Carcinus maenas'' is a common littoral crab. It is known by different names around the world. In the British Isles, it is generally referred to as the shore crab, or green shore crab. In North America and South Africa, it bears the name europ ...

'' and '' Liocarcinus depurator'' being prominent. In six hours, little remained except the limbs of crustaceans and the discs of ophiuroids. The crab ''

Pagurus bernhardus ''Pagurus bernhardus'' is the common marine hermit crab of Europe's Atlantic coasts. It is sometimes referred to as the common hermit crab or soldier crab. Its carapace reaches long, and is found in both rocky and sandy areas, from the Arctic ...

'' was the most likely scavenger to consume ''O. ophiura'' in baited traps.M. Bergmann, S. K. Wieczorek, P. G. Moore, R. J. A. Atkinson (2002)
Utilisation of invertebrates discarded from the Nephrops fishery by variously selective benthic scavengers in the west of Scotland
''Mar Ecol Prog Ser''. 233: 185–198. Retrieved August 10, 2011.

References

{{Taxonbar, from=Q2223690 Ophiuridae Animals described in 1758 Taxa named by Carl Linnaeus